In recent years several types of wireless communication systems have been developed. For example, wireless local area networks (WLAN) are widely spread nowadays, cellular networks, such as UMTS (Universal Mobile Telecommunication System), have gained paramount importance, and, most recently, WiMAX (World Wide Interoperability for Microwave Access) has been developed as a standard-based technology enabling the delivery of last mile wireless broadband access. Most of the new wireless communication techniques provide the benefit of higher bandwidth to its users. With increasing capabilities of wireless communication systems, new services over the wireless link, like video telephony, video streams or high quality audio streams, became feasible. The combination of new wireless communication techniques and new services results in improved availability and convenience for the user.
Many of these services need certain quality of service for being accepted by the users. As additionally high data rates are required, increasing demands on the resources of the access network (AN) emerge. Very often, these requirements were fulfilled by providing enough resources at the AN for handling each possible wireless link at the highest data rate provided by the wireless system. Due to the high costs and due to the higher data rates that are available at new systems, this approach is not acceptable at new wireless communication techniques. Hence, quality of service (QoS) management is introduced in ANs which aims at granting sufficient resources to individual or groups of traffic flows so that they can meet specified performance objectives. These performance objectives include providing sufficient bandwidth or handling data packets with less than a maximum delay or jitter.
There exist a number of different QoS architecture and mechanisms for providing QoS for traffic flows in networks. At ANs, basically two QoS architectures are known in the art: IntServ and DiffServ. At IntServ, resources of AN network entities are allocated explicitly for each data flow. When a data flow is established, the demanded resources of the AN are allocated or reserved. Using DiffServ, resources are allocated to several traffic classes. Each data packet contains a traffic class marker concerning to which prioritisation or queuing of the data packet is defined. Generally, IntServ is preferred at ANs with restricted resources and remarkable variations of network load.
In a general scenario, a mobile node like a user's communication device/terminal, in the following referred to as user equipment (UE) is attached to an AN via points of attachment (PoA). Generally, the access link between UE and PoA is provided by wireless communication techniques. In the access network, substantially cable-based transmission on copper or fibre optic cables is used. As each packet or data flow should be handled according to their respective QoS requirements, these requirements have to be made known to the inner QoS mechanism of the AN. Each entity involved in communication between the UE and its communication partner has to be aware of the QoS requirements. This information is basically exchanged at the allocation of resources.
As standard approach at providing QoS mechanisms at communication between a UE and an AN is to extend the inner QoS mechanism of the AN to the UE. A QoS managing function (QoS MF) is running at the UE and is used at allocation or reservation of resources at the communication path. The QoS MF signals QoS requirements to its PoA which sends QoS signalling to the next hop entity that needs to allocate resources along the communication path. A drawback of this approach arises from the fact that each UE has to be aware of the inner QoS mechanism of the AN. This results in compatibility and security problems. A UE that does not know the inner QoS mechanism of an AN is not able to communicate using QoS. On the other hand the inner has to be exposed to the UE which might be used by attackers at blocking network resources of the AN. Another drawback is the need of connectivity of the UE. If the UE is not attached to a PoA, no QoS signalling can be exchanged and thus no resources can be allocated. The latter drawback is particularly problematic at performing handover of UEs from one PoA to a second PoA. A handover might be reasonable, if the current access link provides poor QoS or if another PoA provides communication at lower costs. At the above-mentioned approach of QoS allocation, a UE has to establish a link to a second PoA in order to perform allocation of resources, while keeping the current link for continued communication.
This problem is solved by handover mechanisms like the media independent handover (MIH) mechanism of the IEEE 802.21 standard draft, which typically allows UEs to perform resource availability checks and resource allocation without establishing a link to a PoA. However, this handover mechanism just refers to the access link, i.e. the link between the UE and the current, candidate or target PoA, respectively. MIH does not support testing of resource availability or allocation of resources at the AN.